For the research, study co-author Jeffrey Ellenbogen of Harvard Medical School recruited 12 self-described sound sleepers to spend three nights in his "comfy" lab.

The first night, the sleepers were treated to quiet conditions. But during the next two nights, scientists bombarded the subjects with several types of sounds—including jet engine roars and toilet flushes—after the people had fallen asleep. (Take National Geographic magazine's sleep quiz.)

Brain wave readings revealed that the more spindles a person had, the more likely he or she could stay asleep through the barrage of noises, Ellenbogen said.

Everybody has spindles, which are controlled by the thalamus, a "way station" that conveys sensory information to other parts of the brain, Ellenbogen said. (Related: "Beyond the Brain" in National Geographic magazine.)

"Now we can leverage this naturally occurring process [of spindle generation] and use that as a tool to prevent the sleeper from disruption," he said. For instance, it may be possible to design a drug that would enhance spindles in light sleepers.

In the meantime, testing a person's spindle activity may help predict an individual's tolerance to noise, Ellenbogen added.

This could help with life decisions, he said, such as: "Should I take the job that puts me in the city, where I'm [in] urban chaos?"

The sound-sleep research will appear August 10 in the journalCurrent Biology.